Eliminate bogus (and harmful) blanking adjustment for load detect.

Instead of always adding blanking to mode lines, use the FORCE_BORDER option
on i9xx hardware where it works, and dynamically add a bit of border if
necessary on i8xx hardware to make load detection work. This may cause
flashing when a usable crtc is not otherwise idle when load detection is
requested.
(cherry picked from commit 6f18300aed1340348c6d395f326061b5315be643)

1 files changed, 75 insertions, 35 deletions

diff --git a/src/i830_crt.c b/src/i830_crt.c
index 6d70f39a..1900dfb7 100644
--- a/src/i830_crt.c
+++ b/src/i830_crt.c
@@ -209,10 +209,8 @@ i830_crt_detect_load (xf86CrtcPtr	    crtc,
     CARD32		    dsl;
     CARD8		    st00;
     int			    bclrpat_reg, pipeconf_reg, pipe_dsl_reg;
-    int			    vtotal_reg;
-    int			    vblank_reg;
+    int			    vtotal_reg, vblank_reg, vsync_reg;
     int			    pipe = i830_crtc->pipe;
-    int			    count, detect;
     Bool		    present;
 
     if (pipe == 0) 
@@ -220,6 +218,7 @@ i830_crt_detect_load (xf86CrtcPtr	    crtc,
 	bclrpat_reg = BCLRPAT_A;
 	vtotal_reg = VTOTAL_A;
 	vblank_reg = VBLANK_A;
+	vsync_reg = VSYNC_A;
 	pipeconf_reg = PIPEACONF;
 	pipe_dsl_reg = PIPEA_DSL;
     }
@@ -228,6 +227,7 @@ i830_crt_detect_load (xf86CrtcPtr	    crtc,
 	bclrpat_reg = BCLRPAT_B;
 	vtotal_reg = VTOTAL_B;
 	vblank_reg = VBLANK_B;
+	vsync_reg = VSYNC_B;
 	pipeconf_reg = PIPEBCONF;
 	pipe_dsl_reg = PIPEB_DSL;
     }
@@ -242,45 +242,78 @@ i830_crt_detect_load (xf86CrtcPtr	    crtc,
     vblank_start = (vblank & 0xfff) + 1;
     vblank_end = ((vblank >> 16) & 0xfff) + 1;
     
-    /* sample in the vertical border, selecting the larger one */
-    if (vblank_start - vactive >= vtotal - vblank_end)
-	vsample = (vblank_start + vactive) >> 1;
-    else
-	vsample = (vtotal + vblank_end) >> 1;
-
     /* Set the border color to purple. */
     OUTREG(bclrpat_reg, 0x500050);
     
-    /*
-     * Wait for the border to be displayed
-     */
-    while (INREG(pipe_dsl_reg) >= vactive)
-	;
-    while ((dsl = INREG(pipe_dsl_reg)) <= vsample)
-	;
-    /*
-     * Watch ST00 for an entire scanline
-     */
-    detect = 0;
-    count = 0;
-    do {
-	count++;
-	/* Read the ST00 VGA status register */
-	st00 = pI830->readStandard(pI830, 0x3c2);
-	if (st00 & (1 << 4))
-	    detect++;
-    } while ((INREG(pipe_dsl_reg) == dsl));
+    if (IS_I9XX (pI830))
+    {
+	CARD32	pipeconf = INREG(pipeconf_reg);
+	OUTREG(pipeconf_reg, pipeconf | PIPECONF_FORCE_BORDER);
+	
+	st00 = pI830->readStandard (pI830, 0x3c2);
+	present = (st00 & (1 << 4)) != 0;
+	OUTREG(pipeconf_reg, pipeconf);
+    }
+    else
+    {
+	Bool	restore_vblank = FALSE;
+	int	count, detect;
+
+	/*
+	 * If there isn't any border, add some.
+	 * Yes, this will flicker
+	 */
+	if (vblank_start <= vactive && vblank_end >= vtotal)
+	{
+	    CARD32  vsync = INREG(vsync_reg);
+	    CARD32  vsync_start = (vsync & 0xffff) + 1;
+
+	    vblank_start = vsync_start;
+	    OUTREG(vblank_reg, (vblank_start - 1) | ((vblank_end - 1) << 16));
+	    restore_vblank = TRUE;
+	}
+	
+	/* sample in the vertical border, selecting the larger one */
+	if (vblank_start - vactive >= vtotal - vblank_end)
+	    vsample = (vblank_start + vactive) >> 1;
+	else
+	    vsample = (vtotal + vblank_end) >> 1;
+
+	/*
+	 * Wait for the border to be displayed
+	 */
+	while (INREG(pipe_dsl_reg) >= vactive)
+	    ;
+	while ((dsl = INREG(pipe_dsl_reg)) <= vsample)
+	    ;
+	/*
+	 * Watch ST00 for an entire scanline
+	 */
+	detect = 0;
+	count = 0;
+	do {
+	    count++;
+	    /* Read the ST00 VGA status register */
+	    st00 = pI830->readStandard(pI830, 0x3c2);
+	    if (st00 & (1 << 4))
+		detect++;
+	} while ((INREG(pipe_dsl_reg) == dsl));
+	
+	/* restore vblank if necessary */
+	if (restore_vblank)
+	    OUTREG(vblank_reg, vblank);
+	/*
+	 * If more than 3/4 of the scanline detected a monitor,
+	 * then it is assumed to be present. This works even on i830,
+	 * where there isn't any way to force the border color across
+	 * the screen
+	 */
+	present = detect * 4 > count * 3;
+    }
 
     /* Restore previous settings */
     OUTREG(bclrpat_reg, save_bclrpat);
 
-    /*
-     * If more than 3/4 of the scanline detected a monitor,
-     * then it is assumed to be present. This works even on i830,
-     * where there isn't any way to force the border color across
-     * the screen
-     */
-    present = detect * 4 > count * 3;
     return present;
 }
 
@@ -352,10 +385,17 @@ i830_crt_detect(xf86OutputPtr output)
 	if (!crtc->enabled)
 	{
 	    xf86SetModeCrtc (&mode, INTERLACE_HALVE_V);
+	    /*
+	     * Give us some border at the bottom for load detection on i8xx
+	     */
+	    mode.CrtcVBlankStart = mode.CrtcVSyncStart;
+	    if (mode.CrtcVBlankEnd - mode.CrtcVBlankStart < 3)
+		mode.CrtcVBlankStart = mode.CrtcVBlankEnd - 3;
 	    xf86CrtcSetMode (crtc, &mode, RR_Rotate_0, 0, 0);
 	}
 	else if (intel_output->load_detect_temp)
 	{
+	    /* Add this output to the crtc */
 	    output->funcs->mode_set (output, &crtc->mode, &crtc->mode);
 	    output->funcs->commit (output);
 	}